This invention relates to a method and apparatus for accumulating information signals for pictures or speech and for supplying the accumulated signals to plural terminals.
Among the signal accumulation and supplying apparatus for picture or speech signals to plural user terminals, there are a television broadcast apparatus and a broadcast apparatus exploiting a cable television (CATV) system.
These systems unidirectionally transmit multi-channel picture and speech signals to terminal devices, and the terminal devices only select a desired one of the multiple channels, while is has not been possible for the terminal devices to request the signal accumulation and supplying apparatus to transmit picture signals desired to be viewed.
Cassette auto-changers, for example, include means for transmitting the information for selecting the picture and speech signals from the terminal devices. However, in order for the cassette auto-changers to comply with requests made by the terminal devices, a number of transmitting devices corresponding to the number of the terminal devices is required, thus increasing the size of the cassette auto-changer and presenting problems in connection with cost, power consumption, mounting space and operational reliability.
Thus there has been proposed a multiple accessing technique of transmitting real-time signals, such as picture and speech signal, to plural users with the aid of IC memories which are semiconductor memories.
As for the multiple accessing technique of transmitting speech and picture signals to plural users with the aid of IC memories, there have so far been proposed the following two methods.
One of the methods resides in time-divisionally according the rights to use the memory to each user, while the other resides in providing each user side with a decoder.
In JP Patent Publication A-5-167544 (1993), there is disclosed an information distribution apparatus for transmitting the information having the contents responsive to plural terminals to the plural terminals comprising a memory for storing the information at locations specified by address signals, address generating means for sequentially generating plural address signals having values corresponding to the requests made by the plural terminal devices and information readout means for reading out information from the memory and supplying the read-out information to the plural terminal devices.
This belongs to the technique of time-divisionally according the rights to use the memory to each user. That is, a number of memory registers corresponding to the number of users are provided in the memory, and the users occupy their own address registers within the time allocated to them in order to freely access the memory. However, since the speed required of the memory is increased with increase in the number of users, there is imposed a limitation on the number of users.
In JP Patent Publication A-59-224897 (1984), there is disclosed a speech signal transmitting device in which the music source stored in a memory is sequentially read as sequentially time-shifted time-multiplexed multi-channel signals so that plural receivers are able to independently hear desired portions of the speech by unidirectional communication from the signal supply side to the signal receivers.
This belongs to the technique of providing each user side with a decoder, that is, a technique of transmitting the totality of high-speed playback signals to the users. Since the transmission channel of a broad frequency range is required, the technique can hardly be used for coping with picture or speech signals of prolonged play time such as those recorded on video discs or video tapes.
In view of the foregoing, it is an object of the present invention to provide a method and an apparatus capable of accommodating an increased number of users and coping with picture and speech signals of longer play time.